guide

Units & colliders

One unit is one meter; colliders track gameplay surface, not visual detail.

Units

1 unit = 1 meter, Y is up, rotations are in radians.
Components multiply their dimensions by unit from useWorld(), so a whole world can be rescaled from one place (<World unit={…}>).

const { unit } = useWorld()
const tableHeight = 0.75 * unit // 75 cm

Colliders

Every component registers its own physics colliders via a Rapier RigidBody. The guiding rule: collider complexity should match gameplay surface, not visual detail. A bookshelf is one cuboid you can’t walk through — not one collider per book.

Shape	When	Example
`cuboid`	Box-like solids	Bookshelf, walls, crates
Several fixed cuboids	Composed structures	Room (4 walls + floor)
Convex hull	Faceted irregular solids	Rocks
Trimesh	Arbitrary surfaces where visual = collision	Terrain

Trimesh is the most expensive — reach for it only when a shape genuinely needs arbitrary geometry (displaced terrain). Prefer cuboids and hulls everywhere else.

Turn on <World debug> to see collider wireframes while building.